METHOD OF ADJUSTING OUTPUT VOLTAGE OF FREQUENCY CONVERTER Russian patent published in 2008 - IPC H02M7/527 

FIELD: electric engineering.

SUBSTANCE: method can be used in induction heating system provided with semiconductor frequency converters while creating systems of several inverters forming direct and back half-waves of current in load. One inverter is brought into adjustment mode. Inverter also has multi-element mating transformer. Primary windings of transformer are connected with corresponding inverters. Secondary windings are connected in series to form voltage summing circuit. Two intervals with different amplitudes of total output voltage U₁ and U₂ of converter are formed: voltage adding interval, at which interval the voltage of corresponding transformer is summed with rest voltages and is applied to load by means of alternate short-circuiting of diagonals of one inverter to be brought into adjustment mode; and short-circuit interval, formed by continuously open state of two adjacent switches of inverter, at which interval the voltage of primary winding of corresponding transformer excludes from summing circuit. Different combinations of durations T₁ and T₂ form several levels of output voltage U_ave determined by ratio of U_ave=1/T(U₁T₁+U₂T₂), where T is period, namely duration of clock period. Combination of states of inverters defines borders of adjustment range of inverter to be controlled. Output voltages of transformers of non-adjusted inverters can be specified by proportional weight coefficients of binary code (1, 2, 4, 8, 16,..) and weight coefficient of inverter to be adjusted equals to 1.

EFFECT: reduced number of non-adjusted inverters; ability to keep former relation of voltages of converter and controlled inverter; reduced dynamic losses; high power characteristics.

2 cl, 3 dwg